As part of a design and light-weighting trend that began back in the 1970s with the oil embargo, plastic use in automotive applications has grown from a meager 70 lb per vehicle at that time to more than 230 lb today. Industry experts predict that the trend will continue, with another 30 lb or more of plastic components installed in each vehicle by the year 2002. This translates into some 1.04 billion lb of engineering plastics alone for automotive uses as the new century gets underway, according to industry research analyst The Freedonia Group (Cleveland).
Why the switch away from traditional materials for automotive applications? "Vehicle light-weighting and energy efficiency will help lower energy consumption and, in turn, air emissions," reports John McAuley, manager of environmental programs for Montell USA (Wilmington, DE). "Moreover, source reduction or less material usage, post-industrial and post-consumer recycling, and use of recycled content resins will greatly contribute to resource conservation." Plastics can best meet these design goals, says McAuley.
In a recent Ford Motor Co. seminar on the company's "Materials Recycling Partnership for the Environment," McAuley stressed that because of key environmental issues facing the auto industry, fewer materials and parts are being used in applications to make disassembly and recycling of post-industrial and post-consumer materials easier.
Ford brought the environmental/recycling message into perspective when the company, along with its former automotive-components maker Visteon, walked off with the Grand Award at last year's Society of Plastics Engineers automotive awards ceremonies. The award-winning program, "Carpets to Car Parts Recycling," uses 25% post-consumer recycled content in all nylon air cleaners installed in Ford's North American cars and trucks. DuPont reclaims the nylon and other materials from used carpeting--enough to cover all floors of the New York World Trade Center and the U.S. Capital Building.
Chrysler also deserves acclaim for its decision to use recycled polyethylene terephthalate (PET) in headliners for the 1999 Jeep Grand Cherokee. Johnson Controls Automotive Systems Group (Plymouth, MI) and Prince Corp. (Holland, MI), a Johnson Controls subsidiary, developed the material, called CorteX(reg), and sold Chrysler on its use. The process involves using recycled carpets and soft-drink bottles.
Since CorteX uses less space than current-generation products, according to its developers, it offers more vehicle interior design flexibility and more room for occupants. In the Grand Cherokee, the material provides additional head-impact protection as an energy-absorber under the headliner.
These recycling efforts illustrate in only a small way why plastics continue to make inroads into the automotive arena. Freedonia analysts list these other advantages for plastics and elastomers versus metals and glass for automotive uses:
- Lighter weight without sacrificing strength.
- Excellent corrosion resistance.
- Low tooling and finishing costs.
- Ability to improve styling and design flexibility.
- Parts consolidation.
Putting plastics to work. Here's a sampling of innovative projects in 1999-model-year cars:
The Beetle is back, and it's creating a buzz among new car buyers across North America. But this is not the same Beetle that provided basic transportation at a bargain price for millions of drivers from the '50s to the '70s. The new Beetle incorporates the latest automotive technology, including dual airbags, front-wheel-drive, four-wheel disc brakes--and 14 applications of engineering plastics, polyurethane foams, and polyurethane raw materials.
The car features engineering plastics in the headlights and taillights, diisocyanate in the auxiliary springs, and a polyurethane coat to protect the finish on plastic and metal components inside and out. Engineering plastics alsoare used in the inner door panels, instrument panel, glove box, and center console. Polyurethane foam resides inside the doors and instrument panel to control noise and vibration.
Bayer Corp. supplied all of the materials. "To have our materials used so broadly in this new version of a classic automobile is indeed a compliment," says H. Lee Noble, president of Bayer's Polymers Div. (Pittsburgh).
Here's another design challenge for polymers: converting an automotive air brake valve from a cast-metal component to molded plastic. The new design had to function identically and be completely interchangeable with the current product. It also had to reduce cost, part count, and assembly time.
Early attempts by the manufacturer to redesign the valve involved replacing a cast-metal body with a molded plastic body made from acetal. However, the material failed to achieve the desired cost reduction. Teaming with UFE Product Engineering (Stillwater, MN), the valve's engineers and UFE technicians re-engineered the product to better utilize the properties of plastics by switching to Capron(reg), a glass- and mineral-filled nylon supplied by AlliedSignal Plastics (Morristown, NJ).
UFE turned to design-for-assembly concepts to optimize the final product design to meet the customer's cost-cutting criteria by:
- Eliminating the mechanical fasteners and O-ring seals by using spin-welding to attach the lower housing to the body.
- Doing away with the separate metal mounting bracket by incorporating mounts into the molded plastic body.
- Optimizing the design us-ing finite-element analysis to determine the stresses caused by internal pressure and external hose loads.
- Developing working prototypes to validate the design.
- Managing the tooling and manufacturing introduction to achieve a manufactur-able solution.
The result: a weight reduction of 60% over the previous design, and a reduction in parts from 16 to six. You can find the new valves on Mack and Navistar trucks.
More sensitive sensors. Lucas Control Systems (Hampton, VA) had a different challenge to meet: protecting the delicate circuitry of a new mini-sized wheel-speed sensor. It accomplished this by using an advanced thermoplastic encapsulation technology.
Mounted on a fixed member close to a car's wheel-bearing seal or another rotating part fitted with magnets, the electronic sensor uses either the Hall- or magneto-resistive effect to determine wheel speed. This, in turn, generates digital signals for antilock braking, traction control, and other automotive systems.
"With assistance from DuPont, we developed an extremely compact, reliable, and economical sensor," says Kim Smith, a principal product development engineer at Lucas. The sensor's lead frame assembly is encapsulated by placing it in an injection mold fitted with retractable support pins and overmolding it with Zytel(reg) nylon resin supplied by DuPont Engineering Polymers (Wilmington, DE). The formulation: a nylon 612 with a 33% glass reinforcement.
The sensor's internal electrical/electronic assembly consists of an IC chip, and a capacitor, and may contain a diode welded to a lead frame. It is terminated through a pre-molded connector covered by overmolding or by lead wire, depending on the application.
Precise positioning of the IC within the envelope proved crucial to accurate speed sensing, according to Smith. The nylon resin avoids displacement or damage to the delicate parts thanks to its ability for slow, low-pressure mold fill at moderate melt temperature.
Sealing out moisture is also critical. The resin's slow crystallization rate helps Lucas achieve complete fill and void-free sealing in areas where the mold's support pins retract. This blocks moisture penetration and avoids the need for a separate sealing step.
The sensor measures 1 inch long by 0.25 inch in diameter. Its size enables it to be mounted in locations where conventional coil-type sensors won't fit.
Initially, Lucas expects to supply the sensors for use in European automobiles with magnets mounted on wheel-bearing seals. Planned developments include modification for use with a toothed wheel that rotates with road wheels, a popular design in the U.S. In the future, Lucas envisions adapting the sensor to provide even greater sensitivity, along with information about direction of rotation.
Instrument panels (IPs) also offer bountiful opportunities for plastics. To reduce weight and cost on IPs and other interior components, Ford switched from a polycarbonate (PC) for its F-Series trucks to a PC and acrylonitrile-butadiene-styrene (ABS) blend. The material, Dow Chemical's PULSE 2000, is the first PC/ABS to be approved under a new Ford global specification.
Ford supplier Visteon (Dearborn, MI) uses the resin primarily for instrument panels and knee bolsters on the popular Ford trucks, resulting in a reduction in cost and weight while still meeting all performance requirements. "Visteon and Ford have a strong commitment to continuous improvements in manufacturing processes, component systems, and finished vehicles," reports Rick Lee, market manager for Dow Automotive (Troy, MI), who helped sell the automaker on the Dow Chemical material. "In this case, they looked for an IP material with an improved cost/performance ratio."
When compared to PC, PC/ABS provides a better melt flow rate, allowing for faster cycle times, Lee explains. Its lower specific gravity produces lighter-weight parts. Both features contribute to further cost reductions.
Looking to the future, Visteon is evaluating PULSE 2100LG, a low-gloss PC/ABS, for unpainted, molded-in-color instrument panel applications on Ford's F-Super Duty truck made in South America. This material could further reduce costs by eliminating paint, Lee notes. To date, the resin has passed all the physical property and part performance tests for this project.
Electronics also comprise a major area for the advancement of plastics. For example, computers that can manage a variety of automotive systems have become almost commonplace in today's cars. VDO (Bebra, Germany) produces and ships these "black boxes" worldwide.
Recently, the company decided to replace the piston in one of its metal and aluminum units with a co-molded thermoplastic that features a metal insert. It selected a polyetheretherketone (PEEK) polymer for the piston, which regulates air flow in engine control systems, and realized significant cost and weight savings.
"Following trials with several different high-temperature thermoplastic polymers, VDO chose PEEK(TM) polymer 450FC30 to provide the reduced friction needed for this elevated-temperature application," reports Kevin Jennings, marketing manager at Victrex USA Inc. (Westchester, PA), which supplied the material.
VDO developed the metal-insert and co-molding process in cooperation with Bavarian-based Matthia Oechsler & Sohn, a company specializing in precision moldings and complete sub-assemblies made in plastics. "Once the metal insert, a bushing, is placed in the mold, PEEK polymer is injected to cover its upper areas," Jennings explains.
The process eliminates any post-treatment and consolidates a previously two-part component into one part, reducing manufacturing costs. "Furthermore," adds Jennings, "it permits a more compact design for space and weight savings, as well as improved function due to the excellent properties of PEEK, which minimize static friction on the piston."
Elastomers also help stretch design opportunities for polymers. Recently, Italian car maker Fiat Spa. (Torino) turned to a thermoplastic elastomer (TPE) for the semi-dynamic interior belt line seals in its Punto models. The TPE replaced an ethylene propylene diene monomer (EPDM) rubber profile, enabling Fiat to lower system cost and reduce weight. The material used: Santoprene(reg) supplied by Advanced Elastomer Systems (Akron, OH).
Ziliani Spa. developed the application with a technical assist from Advanced Elastomer Systems. Ziliani used an innovative system--an in-line flocked strip application on a hot profile--to flock the glass-to-TPE contact surface, creating a low coefficient of friction.
Not only does the system provide an excellent seal that can withstand years of weather extremes, but the flocked surface adds to the aesthetics of the interior belt lines. And the material is 100% recyclable. This combination of properties enabled Fiat to substantially reduce costs by eliminating several assembly steps required for the EPDM profile.
Such applications clearly indicate how plastics continue to move aggressively into the automotive marketplace. For more examples, check out the American Plastics Council's Automotive Center's website at www.plastic-car.com.
And don't be too surprised if you're reading about a production car designed around plastics in the not-too-distant future. Chrysler reportedly has a five-year plan to produce a prototype vehicle for the North American market made from a lightweight, injection-molded plastic structural shell. That work could revolutionize the use of thermoplastics for exterior body panels.
What this means to you
- Use of engineered plastics for automotive applications will grow to more than 1 billion lb by the year 2001.
- Innovative applications for automotive plastics could have equally rewarding uses for design engineers in other industrial segments.
- Automotive technical and research centers at major resin producers provide a valuable assist in the design of automotive components.
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